The overall goal of the proposed research is to elucidate the mechanisms of toxic action of phenoxy acid herbicides at subcellular and molecular levels. Selected as models for comparative studies in this project are 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-tricholorophenoxyacetic acid (2,4,5-T), two well-known herbicides of considerable public concern in environmental health. Central to this research is the evaluation of the hypothesis that the cytoskeleton acts as a major target of insults by these herbicides and, as such, its perturbations or damage may be an important part in the manifestation of cellular injury leading to systemic toxicity or cell death. The proposed investigations will focus on both the molecular mechanisms of herbicide-induced and microfilament (MF) derangement, and the consequences of such perturbations, in particular, alterations in subcellular and molecular events and associations influenced by the cytoskeleton. The specific aims of this project are to seek answers to the following questions. 1. Mechanisms of cytoskeletal injuries induced by 2,4,5-D and 2,4,5-T. a. Are these cytoskeletal injuries due to alterations in the molecular species, phosphorylation state and distribution of microtubule associated proteins (MAPs) and their isoelectric variants? b. What is the role of glutathione metabolism in modulating cytoskeletal perturbations caused by herbicides? c. Do 2,4,5-D and 2,3,5-T act directly on MT and MF in the extracted cytoskeleton incubated in situ? d. Do herbicides perturb the kinetics and pattern of MT reassembly from microtubule organizing center (MTOC)? e. Does prior disruption of MF affects the behavior of MT in forming aggregates and bundles induced by herbicides? 2. Do these cytoskeletal injuries result in alterations in the cytoplasmic location, organization and morphology of organelles such as mitochondria, the Golgi apparatus, endoplasmic reticulum and lysosomes? 3. Does treatment with herbicides result in perturbations to the composition and organization of ht nuclear matrix?